CN1131925C - Method and apparatus for drilling with flexible shaft while using hydraulic assistance - Google Patents

Abstract

The invention discloses a device and a method for applying impact force to a drill bit when a flexible shaft is used to drill a hole in a cased well. The impact force is applied directly to the drill bit rather than through a flexible drilling shaft. A bearing sleeve contacts the piston and is in sliding contact with the tool chamber. A portion of the piston is located in one of the piston chambers and is in sliding contact with the walls of the chamber. When hydraulic fluid flows into the chamber on the opposite side of the piston, the piston moves toward the bit. When the piston moves toward the drill bit, a force acts on the support sleeve, causing the support sleeve to move towards the drill bit. When drilling, this force is transmitted to the drill bit, providing the drill bit with the force required to effectively drill into the material to be drilled.

Description

Drilling equipment and method of drilling through material

technical field

The invention relates to the field of stratum detection around the wellbore, which uses a flexible shaft to drill a hole through the borehole wall and enter into the stratum. More specifically, the present invention relates to extending the life of a flexible shaft by applying force to a drill bit by other means than the flexible shaft.

Background technique

Flexible shafts have been used in drilling for many years. Many drilling systems have been proposed that use a flexible shaft to drive the drill bit. One such system for use in oil and gas production processes is found in US Patent 96458916 (Bond). The patent uses a flexible shaft to operate in a vertical well first, and then drill in a horizontal direction to a large distance from the wellbore to expand the detectable area.

Typically, the purpose of using a flexible shaft is to overcome the space constraints of the drilling equipment. The flexible shaft enables drilling of the borehole to a depth deeper than the headroom of the drilled borehole. For example, in the coal mining process, the depth of the bolt hole drilled on the roof of the coal seam can reach 3 times the thickness of the coal seam. In oil and gas wells, zones require vertical borehole drilling to a distance deeper than the inside diameter of the wellbore. The same applies to cased wells. In this case, the drilling system provides a flexible shaft at the bend in the borehole so that drilling can continue. Importantly, the space available in a cased hole is much less than that required in the aforementioned flexible shaft applications. Even with a coal seam three feet thick, the inside diameter of a cased hole is five inches or less. Therefore, the size of the drilling equipment as well as the flexible shaft must be sufficiently small.

In cased hole applications, a flexible shaft with joints at both ends is installed in a pipe with a fixed curved shape. Joints allow easy coupling of the flexible shaft to its equipment, such as drive motor shafts and drill bits. To achieve drilling, a drill bit not only requires torque to rotate the bit about a central axis (measured in revolutions per minute, or RPM), but also needs to apply an impact force to the material being drilled. This impact force is called Weight On Bit or "WOB" for short. In a flexible shaft drilling system, these two forces are applied to the drill bit through a flexible shaft. The analysis of the motion of the flexible shaft shows that the resultant forces of torque, bending moment and axial force that cause the deformation of the flexible shaft are balanced.

During the drilling of steel casings, it was found that the flex bearings were subject to significant axial stress. These forces will twist the flexible shaft and shorten the effective length of the flexible shaft. Furthermore, due to high stresses, the service life of the flexible shaft is reduced. Not only the reliability of the drilling system requires a long flexible shaft life, but also increasing the allowable number of holes that can be drilled before the drilling equipment is removed to replace a worn flexible shaft also requires a long flexible shaft life. Therefore, it is very important to reduce or eliminate stress elements in the shaft.

Another problem with this system is the passivation of the drill bit. After drilling through the steel casing, the bit must cut a few inches into the cement, and the flexible shaft must continue to apply torque and impact, albeit at lower values. Also, in many cases, it is necessary to continue drilling into rock, typically shale, stony or sandstone. A common component of these rock formations is quartz, a crystalline substance harder than the cutting teeth of a drill bit (except for diamond bits, which cannot be used to drill steel materials). These quartz materials dull the bit, so that higher torque and WOB are required for continued drilling.

While such torque and WOB increases do not create problems in cement and rock formations (lower initial torque and impact), they can create problems in drilling steel casing below. As mentioned earlier, the high impact forces required to drill steel casing can significantly reduce the life of a flexible shaft. Once the drill bit is blunted, the required impact force is further increased. It was found that after drilling through a few inches of sandstone, the bit became blunt and, although driven by a flexible shaft, could not complete the next hole. If one tries to apply the required impact force, the flexible shaft will usually be destroyed.

This problem can be greatly alleviated if the impact force required by the drill bit is applied to the flexible shaft before it enters the hole being drilled, rather than the usual case of applying force to the tail end of the flexible shaft. A number of impact and torque systems have been developed and are described in the literature (G.K. Derby, and J.E. Bevin, "Roof and Floor Development Program for Coal Seams", US Department of the Interior Bureau of Mines, 1978, US Department of the Interior Library). However, these systems are complex in structure and often have reliability problems.

Furthermore, it has been found that in the particular application of the flexible shaft, the life of the flexible shaft of the system is greatly improved if the system only applies the impact force while drilling into the steel casing cement and rock formations. Even with a blunted bit, increased torque and impact when drilling into cement and rock will not reduce flex shaft life.

Therefore, there is a need for a system that can apply high forces to the drill bit while drilling without damaging the flexible shaft.

Contents of the invention

The object of the present invention is to increase the service life of flexible drilling shafts.

Another object of the present invention is to reduce the stress in the flexible shaft while drilling.

A third object of the present invention is to use a device to apply force to the drill bit instead of the tail end of the flexible shaft.

A kind of drilling apparatus according to the present invention, is positioned at the stratum cross-section, drills borehole material, and it comprises: a) a drill bit, contacts with said borehole material; b) a flexible shaft, and said drill bit c) an excitation device, connected to said flexible shaft, rotates said flexible shaft and drill bit when drilling; and d) an impactor, which directly supplies force to said drill bit, to improve the drill bit In order to improve the efficiency of penetrating the drilled material, the impactor includes piston means for directly supplying force to the drill bit.

According to a method for drilling through materials of the present invention, the drilling equipment used includes a drill bit, a flexible drilling shaft, and a device for applying force to the drill bit, and said method comprises the following steps: a) using the flexible drilling shaft to The rotary means rotates the bit; b) brings the bit into contact with the material to be drilled; and c) applies an impact force directly to the bit by means of a piston means as the bit rotates, whereby the bit advances into the material to be drilled.

The present invention prolongs the service life of the flexible shaft by applying impact force (weight-on-bit) to the drill bit in the formation at the point of contact between the drill bit and the well wall or casing. Impact force is provided by a hydraulic piston system. The drill bit and its attached flexible shaft are connected by bearings which are housed in bearing housings or similar devices. The bearing sleeve is connected with the piston. When drilling, the piston moves toward the well wall, thus generating impact force, which is transmitted to the bearing and drill bit through the bearing sleeve. Force from the piston is applied to the bit, causing the bit to penetrate the steel casing. This technical solution directly applies force to the drill bit, rather than applying force to the drill bit through a flexible shaft as in the prior art. Note that this technical solution still applies torque by means of a flexible shaft.

The present invention increases the service life of the flexible shaft by reducing peak stresses. Peak stresses occur when drilling into steel casing. This works by providing a piston stroke to the piston system so that piston force is applied to the bit only when the bit penetrates the steel casing. After drilling through the steel casing, the piston (and housing and bearings) return to apply force to the drill bit through the flexible shaft to complete the remainder of the drilling operation.

The system of the invention has a simple and firm structure, and can be installed in a tool bag with a small diameter and lowered into the casing. This system greatly improves the drilling efficiency of the flexshaft from the point of view that the torque and impact force are applied to the tail end of the flexshaft. At the same time, the system also overcomes the difficulties in the application of the impact system and the torque system.

Description of drawings

Figure 1 is a schematic diagram of formation detection equipment used in a cased well.

Fig. 2 is a schematic diagram of an embodiment of the present invention with only a single piston in the longitudinal section.

Figure 3 is a detailed view of a single piston embodiment of the present invention.

Figure 4 is a detailed view of the bearing portion of the present invention.

Fig. 5 is a flowchart of the method of the present invention.

Figure 6 is a view of an embodiment of the dual piston system of the present invention.

Detailed ways

Fig. 1 shows the connection relationship of the present invention in a downhole formation detector, which is used for drilling, sampling and plugging casing in a cased well. This cased borehole detector is found in patent application 202,634 filed concurrently with the present invention and related to US Patent 5,195,588. At the heart of the invention is the drilling of cased wells. The invention is described in the context of drilling a cased well. In FIG. 2 , a drill head 1 is connected to a flexible shaft 2 . The length of the drill bit is greater than the wall thickness of the drilled casing, and the diameter is greater than the diameter of the flexible shaft 2 . The impact bearing 3 is installed in the support sleeve 4 . The impact bearing can apply force to the drill bit by squeezing the drill bit shoulder 1a between the drill bit and the flexible shaft. Impact bearings allow the piston to apply force to the rotating bit without excessive frictional losses. The support sleeve 4 is driven by the piston 5 and can move up and down along an axis parallel to the flexible axis. The length 6a of the piston cavity must be slightly larger than the wall thickness of the casing so that the force can be transmitted to the drill bit during the whole process of drilling the casing. . The flexible shaft moves along the guide groove 7 with a certain geometric shape. The geometry of the channel can be a pair of discs with hooks joined together by hooks. The geometry of the channel allows the flex axis to change from perpendicular to the borehole axis to parallel to the borehole axis. The guide groove 7 is located in the inner cavity 8 and has some other characteristics. The drill bit is driven by a flexible shaft, enabling the drilling depth to be greater than the inner diameter of the drilling equipment. A transmission and drive system can apply torque and impact to the flexible shaft in Figure 1.

As shown in FIG. 3 , the piston end surface 5 a is located in the piston cavity 6 , and the piston rod 5 b is connected to the supporting sleeve 4 through a bolt 9 . The support sleeve 4 is slidingly coupled with the piston chamber, so the support frame can move with the movement of the piston. The support 3 is located in the support sleeve 4 . The support is also in contact with the drill bit 1 . While drilling, hydraulic fluid fills the piston chamber 6a. When the hydraulic fluid fills the piston cavity, the hydraulic fluid forces the piston to move toward the drill bit and the borehole wall. When the piston moves, the force acts on the supporting frame, so that the supporting frame moves along the moving direction of the piston. When the piston moves, the piston force is transmitted to the bearing 3 through the supporting frame. The bearing 3 is in contact with the drill bit 1, and the same force is applied to the drill bit to make the drill bit drill through the casing. After drilling through the casing, the piston force is terminated and the piston returns to the tool cavity. Flexible shafts provide the torque and impact required to complete drilling operations.

The details of the bearing 3 in FIG. 3 are shown in FIG. 4 . The bearing 3 has an inner face 10 , an outer face 11 and a ball 12 . The inner end face 10 is in contact with the drill bit. The diameter of the drill bit is greater than the diameter of the flexible shaft 2 . The inner end face 10 contacts the drill bit at the gap of the diameter difference between the drill bit and the flexible shaft. The outer end face 11 is in contact with the bearing sleeve 4 . The force of the piston 5 is transmitted to the inner end surface 10 and the drill bit 1 through the outer end surface 11 and the ball 12 .

A standard drilling sequence is to drill through the casing first, then the cement sheath, and finally the formation rock. The sequence is shown in Figure 5. The drive system is transmitted through the flexible shaft to allow the drill bit to drill at normal speed (40 in the figure). Then, the drill bit is in contact with the sleeve pipe, and simultaneously moves upward to transmit the drive system, as shown in Figure 2; the piston moves outward and rightward, as shown in Figure 2 (41 among the figures). After the drill bit was in contact with the sleeve pipe, the required impact force for normal cutting was applied to the back of the drill bit by the piston 42 (42 among the figures). By applying force to the drill in this way, it is not necessary to apply force through the flexible shaft. However, it is necessary to adjust the movement of the system in order to make the transfer system coincide with the movement speed of the piston. In this way, when drilling into the casing, the flexible shaft is neither in tension nor in compression, and is in a neutral state. The next step 43 in the sequence is to drill into the cement sheath and formation rock. During these steps, rotational and impact forces are applied through a transmission drive system. It is feasible to apply impact force through the drive system at this time, because the drilled material is relatively weak, so the flexible shaft is only subjected to low torsional and compressive loads.

Another embodiment of the present invention is shown in Fig. 6, when drilling, a double piston is used to apply impact force to the drill bit. This embodiment is more suitable where the channel geometry is limited in the previous embodiments. Piston arms 15 and 16 are located on opposite sides of the drill bit. The piston arm and the piston end face 5 are displaceable in the piston chamber 21 . Inside the piston cavity are piston chambers 18 and 18a. Like the previous embodiment, the drill bit is connected to the inner end face 10 of the bearing by the flexible shaft, the outer end face 11 and the spheroid 12, and the piston action force is transmitted to the drill bit through the support sleeve 17. As previously mentioned, the inner end surface 10 of the bearing is in contact with the drill bit. Note that the drill diameter at the contact point is smaller than the drill diameter at the rest of the drill. This reduction in outer diameter allows the drill bit to have a contact surface with the inner end face 10 . The outer end face 11 is in direct contact with the bearing sleeve 17 . The bearing sleeve 17 is also in contact with the piston arms 15 and 16 . Furthermore, the bearing sleeve is in sliding contact with the bearing chamber 19 .

The movement of the piston is controlled by extending and retracting the piston by hydraulic pressure. During drilling, hydraulic fluid enters the piston chamber 18 through 22 and the cylinder extends. The fluid moves the piston 5 towards the drill bit. Impact force acts on the piston, and the piston moves toward the drill bit, forcing the support sleeve 17 to move toward the drill bit. When drilling, the movement of the support sleeve exerts an impact force on the drill bit. After an impact force is applied to the drill bit, the fluid flows into the retraction hole 23 of the hydraulic cylinder. The piston is thereby returned to the piston chamber 18a. This technical solution forces the piston away from the bit, allowing the hydraulic fluid in the cylinder 18 to flow back into the cylinder extension hole 22 . An "O" ring seal is provided within the piston seal to prevent fluid from flowing between chambers 18 and 18a.

The present invention can also apply impact to the drill bit at extended depths in the formation by varying the desired piston stroke or piston chamber length. The method and device have significant advantages over the prior art. The invention has been described in a preferred embodiment. However, the present invention is not limited thereto. Any changes, variations and modifications to the basic design of the present invention do not depart from the concept of the present invention. Moreover, such changes, changes and modifications will be obvious to those skilled in the art having the benefit of the foregoing technology, and all such changes, changes and modifications are within the scope of the present invention.

Claims (14)

1. A kind of drilling equipment is located in the cross-section of the formation and drills into the hole material, which includes: a) a drill bit (1), in contact with said borehole material; b) a flexible shaft (2) connected to said drill bit; c) an excitation device, connected with said flexible shaft (2), rotates said flexible shaft and drill bit (1) when drilling; and d) A hammer which directly supplies force to said drill bit (1) to increase the efficiency of the drill bit in said drilled material, said hammer comprising piston means for directly supplying force to said drill bit. 2. The drilling equipment according to claim 1, characterized in that said drilling equipment is mounted on a cable that is lowered into the well. 3. The drilling equipment according to claim 1, wherein said piston device comprises: A piston (5) is used to apply impact force to said drill bit (1); A support sleeve (4/17), connected with said piston, transmits said impact force to the drill bit; as well as The bearing device (3) is located between said drill bit (1) and said support sleeve (4/17) and is in contact with it. 4. The drilling equipment according to claim 1, characterized in that said piston device comprises a base (5a), a piston rod (5b) and a support sleeve (4/17), said piston rod and The support sleeves (4/17) are connected, the base body is located in a chamber (6a), and the piston base body (5a) is in sliding contact with the piston chamber (6a). 5. The drilling equipment according to claim 4, further comprising hydraulic fluid to apply force to said piston base (5a). 6. The drilling equipment according to claim 5, characterized in that said piston chamber (6a) has an opening through which fluid can flow in and out. 7. The drilling equipment according to claim 4, characterized in that the inside of the chamber is divided by the piston base (5a) to form two piston chambers (18, 18a). 8. Drilling equipment according to claim 7, characterized in that each piston chamber (18, 18a) has at least one opening through which fluid can flow into and out of said piston chamber. 9. The drilling apparatus of claim 1, wherein said piston means comprises a plurality of pistons. 10. The drilling equipment according to claim 9, characterized in that each piston (5) includes a base body and a piston rod (15, 16), and said piston device also includes a support sleeve (17), so Said piston rods are connected to said support sleeves (17), and each of said bases is located in a piston chamber and is in sliding contact with the wall of the respective piston chamber. 11. Drilling equipment according to claim 10, characterized in that each piston chamber is separated by its internal piston base to form two piston chambers (18, 18a). 12. Drilling equipment according to claim 11, characterized in that each piston chamber (18, 18a) has at least one opening (22, 23) through which fluid can flow into and out of said piston chamber. 13. A method for drilling through materials, the drilling equipment used includes a drill bit (1), a flexible drilling shaft (2), and a device for applying force to the drill bit, said method comprising the following steps: a) rotating the drill bit (1) by means of a rotating device through the flexible drilling shaft (2); b) bringing the drill bit into contact with the material to be drilled; and c) When the drill bit rotates, the piston device is used to directly apply an impact force to the drill bit, so that the drill bit advances into the material to be drilled. 14. The method of claim 13 wherein said piston means comprises a plurality of pistons.

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